JPH03112187A - Manufacture of printed-wiring board - Google Patents

Abstract

PURPOSE:To improve connection reliability by placing a specified metal wire in the cavity of a planar cavity forming mold in the direction of plate thickness in advance and by providing circuit patterns on both surfaces of a substrate obtained by injecting a thermosetting resin composition. CONSTITUTION:A mold consists of an upper mold 1 and a lower mold 2 and a planar cavity 3 is formed. The plate thickness is adjusted by a spacer 4. A metal wire 5 is retained at a specified position of two heat resistant supporting plates 6 through the spacer 4 and is set in the mold and a thermosetting resin is injected and cured. A substrate where the metal wire is exposed onto the surface can be obtained by opening the mold and eliminating the supporting plate 6. After that, a printed-wiring board can be obtained by forming a circuit pattern on the surface of the substrate. A through-hole forming process is abbreviated and a printed-wiring board which is superb in connection reliability can be obtained. As the thermosetting resin composition, an epoxy resin employing a phenol resin as a curing agent is effective.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing printed wiring boards used in electronic devices and the like.

[Conventional technology]

Conventionally, printed wiring boards used in electronic devices, etc. are made by impregnating paper or cloth with phenol resin, epoxy resin, etc., drying, cutting, laminating a predetermined number of sheets, placing copper foil on them, and then forming them under heat and pressure using a press. It is obtained by applying circuit processing such as etching to a copper-clad laminate made of copper. As described above, since the molding process is numerous and complicated, production efficiency is poor, and the base material, resin, interlayers, etc. tend to absorb moisture during the process, leading to a decrease in the heat resistance of the substrate. In addition, many foreign substances are generated due to cutting etc. performed during the molding process, which causes poor appearance and deterioration of electrical characteristics.

In addition, in wiring boards having double-sided boards or higher, through-holes formed by plating drilled holes are used as conduction means between patterns. For this reason, the quality of personnel during drilling becomes a problem, and the inner wall of the hole is rough, which causes defects around the plating, and smear, which causes poor conductivity, tends to occur.Furthermore, the unit cost of the drill is high, and production due to the drilling process is involved. A decrease in efficiency also occurs, leading to an increase in the cost of printed wiring boards.

[Problem to be solved by the invention]

One method for solving these problems is to form the substrate by injection molding. By using this method, production efficiency is greatly improved, and by using a thermosetting resin as the material, it is expected that the ease of holding the substrate will be improved.

In particular, since paper, cloth, etc. do not enter the board, it is very advantageous in improving electrical properties such as heat resistance and copper migration, which have been problems in the past.

Until now, thermoplastic resins such as polyetheretherketone, polyethersulfone, and polyetherimide have been mainly used as materials for injection molded substrates, but the resin unit cost is high and the adhesive strength with metal foil etc. is low. There is. Furthermore, since the molding temperature is extremely high at around 300°C, there are also problems with dimensional stability and the like.

On the other hand, as an example of using thermosetting resin, JP-A-58-7
There are publications such as No. 7276 and No. 5B-77285,
Regardless of thermoplastic or thermosetting resin, when through-hole holes are formed in advance during injection molding, the inner walls of the holes may be smooth, which can easily cause defects around the through-hole plating. It is thought that the hole diameter will become smaller as the density increases, making it difficult to mold a narrow bottle using a molding method using such a pin stand mold.

The present invention was made in view of this situation, and provides a method for manufacturing a printed wiring board that can omit a through-hole forming process such as drilling and has excellent connection reliability.

Of course, the method for producing a printed wiring board of the present invention involves placing a predetermined metal wire in the board thickness direction in advance in the cavity of a molding die that forms a flat cavity, and then injecting a thermosetting resin composition. A printed wiring board is produced by forming circuit patterns on both sides of the cured substrate.

The present invention will be explained in detail below.

As thermosetting resins, phenolic resins, epoxy resins,
Any resin such as polyimide resin, unsaturated polyester resin, or triazine resin may be used, and several types may be used in combination. In particular, systems in which epoxy resin is blended with phenol resin as a curing agent exhibit excellent properties such as heat resistance.

In addition, by blending various fillers with such resin systems, it is possible to further improve impact resistance, fracture strength, dimensional stability, etc. Typical fillers include silica, alumina, and mica. , whiskers, etc., and if necessary, thermoplastic resin powder and the like can also be used as fillers.

Metal wires placed in advance in the cavity include gold, silver, copper,
Nickel, stainless steel, etc. are used, but any material with excellent electrical conductivity may be used. Thin wires of various metals, copper wires, etc. have low strength, so the surface of steel wires, etc. should be coated with metals such as copper. A coated or plated metal wire may be used, and since there is a concern that migration silane may be generated in the wire, a metal wire whose surface is coated or plated with nickel or the like may be used.

In order to improve the adhesion between resin and filler, metal wire, etc.
A surface treatment agent such as a silane coupling agent may be added to the resin.

Furthermore, by adding an arbitrary surface treatment agent, it is expected that the adhesion to circuits to be formed later will be improved. The silane treatment agent may be any epoxy silane, amino silane, cationic silane, mercapto solan, or the like.

FIG. 1 shows an example of a mold used in the present invention. The mold is configured such that a flat cavity 3 is formed by an upper mold 1 and a lower mold 2, and the plate thickness is adjusted by a spacer 4.

The metal wire 5 is held in advance at a predetermined position between two heat-resistant support plates 6 via a spacer 4, and then set in a mold, and a thermosetting resin is injected and hardened. Next, the mold is opened and both support plates 6 are removed to obtain a substrate with the metal wires exposed on the surface, and then a circuit pattern is formed on the surface of the substrate to obtain a printed wiring board.

(Example) The present invention will be further explained below based on Examples.

Example 1 IESCN-195, (orthocresol crucible rank type epoxy resin) 80 parts by weight (product name:
(manufactured by Sumitomo Chemical ■) HP-80ON (phenol novolanque resin) (Product name: Hitachi Chemical ■!! i5) 20 parts Silica 75 parts by weight Palladium chloride 3 parts by weight Carvana wax
Dual Electric Part A-187 (Epoxy Silane) (Product Name: Nippon Unica C Co., Ltd.) 2 parts by weight After thoroughly kneading the above compound, 1
Copper wires with a diameter of 0° were placed in the thickness direction of the plate, and the mold shown in Fig. 1 was used to transfer mold the wires to 160"C for 190 seconds.
After curing for 22 hours at °C, a copper wire-containing substrate having a thickness of 1.6 mm and a square size of 200 W was obtained. At that time, the copper wire was fixed using tetrafluoroethylene resin plates on both sides of the spacer.

Example 2 BREN (phenol novolac type brominated epoxy resin) 80 parts by weight (product name: Meiso Kagaku ■) 20ffi parts alumina hydroxide
75 parts by weight palladium chloride
3 parts by weight Carbanawanx
2 parts by weight Kr3M403 (epoxy silane) (trade name: manufactured by Shin-Etsu Chemical ■) 2 parts by weight Molding was carried out in the same manner as in Example 1 to obtain a stainless steel-containing substrate.

Example 3 Diaminodiphenylmethane was used as the curing agent in Example 1 instead of the phenol novolak resin.

Example 4 Example 1! A copper wire whose surface was coated with a mercaptosilane treatment agent was used.

Further, after polishing the surfaces of the metal wire-containing substrates obtained in Examples 1 to 4, a circuit pattern for connection reliability testing was applied by an additive method.

Comparative Example 1 A ginandiamide curing group epoxy resin face with a thickness of 0.
After impregnating a 2 am glass cloth, it was dried at 140°C for 5 minutes to obtain a prepreg. This prepreg was laminated with 8 pieces, 35 μm copper foil was placed on both sides, and heated to 170°C 190°C.
A double-sided copper-clad laminate with a thickness of 1.6 cm was obtained by heating and pressure forming for 1 minute. This board was drilled using a wiring board drill with a drill diameter of 1.0 ms at a rotation speed of 60,000 rpm and a feed rate of 3.
After drilling holes at 000 nv/s+in and performing through-hole plating, a test pattern for connection reliability was processed.

Using the printed wiring board thus obtained, through-hole connection reliability was evaluated by MIL standard 107 and hot oil tests.

To evaluate the connection reliability according to MIL standard 107, one board is repeatedly placed in the atmosphere at 5℃/30 minutes and 125℃/30 minutes and the resistance value is measured.If the resistance value does not increase after 500 cycles, it is OK. If it increased, it was judged as NG.

Evaluation of connection reliability by hot oil test
After repeating the process of immersing in hot oil at 60°C for 10 seconds, draining the water, and immersing in cold water for 10 seconds for 50 or more cycles, if the resistance value did not increase, it was judged as OK, and if it did, it was judged as NG.

The results are shown in Table 1.

Table 1 Evaluation results Examples 1 to 4, which include metal wires formed by injection molding, have very good production efficiency and are superior in connection reliability compared to Comparative Example 1, which is a conventional laminate plated with through-holes. I understand.

[Effects of the Invention] As is clear from the explanation below, the printed wiring board of the present invention has higher connection reliability than the prior art and improves production efficiency.

[Brief explanation of drawings]

The first is a cross-sectional view of a mold used in the method of the present invention. Explanation of symbols 1゜ Upper mold 2゜ Lower mold 3゜ cavity 4゜ spacer 5゜ metal wire 6゜ support plate 7゜ sprue

Claims (2)

[Claims] 1. A predetermined metal wire is placed in advance in the plate thickness direction in the cavity of a molding die that forms a flat cavity, and then a thermosetting resin composition is injected and cured to form a circuit pattern on both sides of the obtained substrate. A method for manufacturing a printed wiring board, comprising: 2. 2. The method for manufacturing a printed wiring board according to claim 1, wherein the thermosetting resin composition is an epoxy resin using a phenol resin as a curing agent.